As per Chicago Consulate of India, PIO cards are being discarded. See this link for details:

" As the last date for conversion of PIO Cards in to OCI cards i.e. June 30, 2017. is approaching near, all PIO card holders are required to convert these cards into OCI cards by this deadline.The Conversion of PIO cards in to OCI cards will be done free of charge(Gratis) for applications submitted until June 30, 2017."“Those who had applied for OCI card more than 3 months ago but have not as yet received their OCI cards may send email(s) mentioning therein Reference No. starting with USAC…. to the Consulate at oci@indianconsulate.com.”

Those who are applying for conversion of PIO card in to OCI card or reissue of OCI card are required to submit only the following documents, along with their application forms:

a) A copy of the valid passport.

b) a copy of PIO card/OCI card.

The OCI card is a smart card which will facilitate quicker immigration clearance at the ICPs and also for obtaining various consular services from the Indian Missions. For those residing in India, it will facilitate in availing various services in India.

The applicants may submit the applications for OCI card in lieu of PIO card to the Indian Mission/FRRO concerned within the jurisdiction of his/her place of residence.

While the grant of OCI card in lieu of PIO card will be on gratis basis, the applicants will have to bear only the postages and service fee wherever applicable.

In cases of erstwhile PIO cardholders, the new foreign passport number (when they get a new passport) will continue to be endorsed on the existing PIO card till the person concerned is issued an OCI card in lieu of the PIO card.

NOTE: All applications along with relevant documents and the requisite fee should necessarily be sent to COX and Kings Global Services, USA. The applications sent to the Consulate will not be entertained.

At the inaugural session of GOPIO/PBD, Minister
for overseas Indian affairs (MOIA) Vayalar Ravi announced the
merger of the Overseas Citizens of India (OCI) and People of Indian
Origin (PIO) to a single card. The minister made this announcement
at the inaugural session of the 11th edition of the Pravasi Bharatiya
Divas (PBD), the NRI conclave that began in Kochi on January 7,
2013. In general, PIO cards are issued to Indians who have been
staying abroad for couple of generations while OCI cards are given
to those who are more recent migrants and have taken citizenships
in other countries. The OCI cards are practically visas that enable
its holders to enter India for an indefinite period, while PIO
card holders have to apply for separate visas.

The merging of these
two cards could make PIO card holders also eligible for the benefits
that are enjoyed by OCI card holders. Minister Ravi said the proposed
amendment to the Emigration Act 1983 had been circulated to other
ministries for comments. Once the comments are received, the bill
would be sent to the Prime Minister for approval. Subsequently
the cabinet has to approve it before it is placed before the Parliament.